The present invention relates to the production of coated abrasives and particularly to the production of coated abrasives having a mesh backing. For the purposes of this invention a mesh is to be distinguished from other fabrics by the area of open space, (that is the space not occupied by the yarn), per unit area. In a mesh product the open space represents at least about 20% of the surface area of the fabric. These mesh-backed products are used in the form of discs, sheets or belts for rough cleaning operations such as floor sanding and cleaning of grills. The products are based on an open woven or knit structure, with leno weave and raschel or marquisette knits being the most frequently used. These have the appearance of screens rather than cloths and it is important that they retain this screen appearance, and hence porosity, even when formed into the final abrasive product. The mesh of the untreated backing is therefore very open with voids representing at least about 20% and more preferably at least 30% of the surface area of the untreated backing. Typically there are from about 12 to 25 yarns per inch in both the warp and cross directions using yarns with a denier from about 70 to about 600. Clearly the thicker yarns are used when the number of yarns per inch is at the lower end of the range to preserve the open character of the mesh. Typical structures have the following characteristics:
______________________________________ DENIER STYLE YARNS/INCH WARP CROSS ______________________________________ marquisette/leno 15 .times. 15 420, 600 marquisette 24 .times. 24 140, 260 marquisette 18 .times. 18 210, 420 raschel 13 .times. 16 70, 70 ______________________________________
Typically the greige mesh material is pre-treated with a finish, such as one based on an acrylic polymer, to make it stiffer and to protect it against the phenolic resin commonly used as the maker coat which renders the fabric brittle. After the finish has been applied and dried, the mesh is given a maker coat followed by the application of abrasive grain, usually by electrostatic deposition. The maker coat is then at least partially cured and a size coat is applied. This too is cured. The sequential drying or curing of the finish, maker and size treatments typically stretches into many hours and this means that very large volumes of "goods in process" need to be maintained. This is particularly true when the maker and size coats are based on phenolic resins as is most frequently the case.
It has now been found possible to compress these operations considerably and even eliminate the mesh pre-treatment, or "finishing", operation altogether. This permits a much more streamlined operation without sacrifice in the quality of the product obtained. The present invention therefore provides a way to produce high-quality, mesh-backed products by an efficient abbreviated process.